Denture adhesives are used to assist a denture's ability to adhere to the gums. Denture adhesives are typically characterized as contributing an adhesive function once exposed to the moisture in a person's mouth and dissolve in the mouth over the course of a day.
A conventional approach is to provide an adhesive material made of a resin in the form of a powder or paste, which can be either natural or synthetic. Each time a user needs to apply a denture to the gum, the user takes the required amount of a denture base stabilizing material from a tube in the case of a powder or paste. Conventional denture adhesives in the form of pastes and powders are highly hydrophilic and readily absorb moisture forming an adhesive gel. One example is conventional Gantrez-based denture adhesives, which are applied to the denture and activated by saliva when the denture is first inserted into the mouth. These pastes and powders can be problematic for denture users. Once inserted, force is applied to the denture in order to spread the paste or power and ensure a snug fit of the denture to the gums. The force of application will cause the gums to displace the paste or gel that is formed and these adhesives will typically ooze or squirt out the side of the denture. This is known as primary ooze and is considered by many denture users as objectionable. Pastes and powders can be difficult to use because they require the denture wearer to ensure that the paste or powder is uniformly applied and in the right amount. Similar and other types of soft denture liners or adhesives have been disclosed in U.S. Pat. Nos. 5,061,182, 5,075,107, 5,436,283, and 5,513,988.
One approach for solving the problems of conventional denture adhesives is to provide a denture liner with mucoadhesive properties. U.S. Pat. No. 7,312,256 attempts to resolve known deficiencies in the art by providing a denture liner with a hydrophobic polymer component, such as polyethyl methacrylate, an esterified copolymer of methyl vinyl ether and maleic anhydride, polyvinyl acetate that inhibits the liner from absorbing moisture, a plasticizing component such as glycerol triacetate, an adhesive component such as sodium carboxymethylcellulose or polyethylene oxide.
Another approach, disclosed in U.S. Pat. Nos. 6,583,225, 6,706,817, and 7,288,597, is to form a hydrogel through the cross-linking reaction between an acidic polymer, particularly copolymers of maleic anhydride or maleic acid, and a comonomer, e.g. an alkylvinylether, with a suitable crosslinking agent, such as glycerol, in the presence of an esterification or amidization catalyst, such as sulfuric acid. The disclosed hydrogel is a covalently bound, ester and/or amide/imide crosslinked hydrogel that is extremely swellable in the presence of moisture. This hydrogel would be tacky in the unswelled state, but tackiness diminishes as swelling increases. Such a product would not function effectively as a denture adhesive because any significant swelling upon exposure to saliva would adversely affect adhesion and bite. As a result, an additional layer or component of a conventional denture adhesive would likely need to be included with the hydrogel to ensure proper adhesion of the denture to the gums.
U.S. Pat. No. 7,008,976 discloses a denture adhesive composition comprising mixed salts of an alkyl vinyl ether-maleic acid or maleic anhydride copolymer and/or terpolymer with isobutylene. While the denture adhesive is said to have improved adhesion, a non-adhesive self-supporting layer is used with the denture adhesive to maintain strength and provide integrity for the adhesive in the presence of water and/or saliva.
Thus, despite the above-noted technologies as well as many others, a need still exists for denture adhesive compositions providing improved hold. It is an object of the present invention to provide a hydrogel with improved adhesive properties to serve as a denture adhesive. It is another object that such a hydrogel have an immediate or quick onset of adhesive action and avoids the deficiencies associated with primary ooze. It is a further object of the present invention that such a hydrogel has a dry tack. It is still a further object of the present invention to provide a hydrogel denture adhesive that is resistant to dissolving over an extended period of time in the presence of water so as to provide an adhesive with an extended lifetime for effective use.